Recaptcha Enterprise API error when creating assessment - php

Question

I am trying to implement Recaptcha Enterprise, I get the userToken and am attempting to create an assessment but when sending the information get the following response:
{
"error": {
"code": 400,
"message": "Invalid JSON payload received. Unknown name "{JSON SENT}": Cannot bind query parameter. Field '{JSON SENT}' could not be found in request message.",
"status": "INVALID_ARGUMENT",
"details": [
{
"#type": "type.googleapis.com/google.rpc.BadRequest",
"fieldViolations": [
{
"description": "Invalid JSON payload received. Unknown name \"{JSON SENT}' could not be found in request message."
}
]
}
]
}
}
My php curl file:
<?php
$token = $_GET["token"];
$secret = "SECRET_ID";
$url = "https://recaptchaenterprise.googleapis.com/v1/projects/{project_id}/assessments?key=" . $secret;
$curl = curl_init($url);
curl_setopt($curl, CURLOPT_URL, $url);
curl_setopt($curl, CURLOPT_POST, true);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
$headers = array(
"Content-Type: application/x-www-form-urlencoded",
);
curl_setopt($curl, CURLOPT_HTTPHEADER, $headers);
$data = ['event' => ['token' => $token, 'siteKey' => $secret, 'expectedAction' => 'verify']];
curl_setopt($curl, CURLOPT_POSTFIELDS, json_encode($data));
$resp = curl_exec($curl);
curl_close($curl);
echo ($resp);
My Json
\"{\"event\":
{\"token\":\"TOKEN\",
\"siteKey\":\"SITE_KEY\",
\"expectedAction\":\"verify\"}
}\"
I have tried consulting the enterprise docs but have been unsuccessful. Any and all help would be appreciated.

Answer 1

For the call to googleapis.com you'd have to use an api key, not the site key. Use the site key (your $secret) only where you build the $data array.
You are sending JSON to google, so the Content-Type should be 'application/json; chartype=utf-8'.
In case you are also posting JSON from your website to this php, then you'd need to use
$json=file_get_contents('php://input');
$jdata=json_decode($json);
to retrieve the data, not $_GET[]. Then you could address:
$token=$jdata->token
$action=$jdata->action